The invention relates to adhesive compositions on the basis of inorganic binder (water glass) and may be used in industry and household for adhering ceramic or natural stone tiles or other coatings to concrete and plastered wall, ceiling and floor surfaces, for inner and outer finishing of residential and public buildings.
RU 2131447, Jun. 10, 1999, reports of adhesive composition comprising from 38 to 42% w/w sodium silicate solution (water glass), filler (34 to 36% w/w marble powder), 2% w/w sodium sulfide and the rest is talc. This adhesive composition adheres wide range of materials such as metal, wood, tiles, silica glass, linoleum, etc.
This adhesive composition has several considerable drawbacks:
poor water resistance because of water soluble compounds formed during solidification of sodium silicate solution;
low stability of viscosity and adhesive properties when the composition stored. The reason is adhesive composition contains sodium sulfide, which initiates crystallization process under prolonged storage at varying temperature. Crystallization increases composition viscosity, moreover composition segregates to liquid (water glass) and solid (marble powder) phases. This infringes the reproducibility of adhesive layer strength.
SU 251737, Sep. 10, 1969 discloses the adhesive composition comprising (in percent by weight) from 2.5 to 3.0 silicate glue, from 90 to 92 carbamide-phurphurol-formaldehyde resin, from 1 to 1.5 carboxymethylcellulose, 3.0 to 3.5 dextrim. The composition has good adhesive properties. It stays active for 2 to 3 days and dries within 8 to 10 minutes. However due to short activity and drying time this adhesive composition has only limited applications, for fixing labels on polyethylene packages mainly.
SU 1092939, Oct. 20, 1995 reports of adhesive composition for adhering metal, ceramic, glass and electrotechnical steel. It comprises (in percent by weight) from 19 to 28 sodium silicate, 10 to 14 aluminium hydroxide, 7 to 12 sodium hydroxide, 25 to 29 kaolin, 2 to 5 titanium dioxide, 1 to 3 kizelgur, 18 to 27 water. This adhesive composition has enhanced thermostability and efficiency at high temperature although it solidifies at temperature from 250 to 300xc2x0 C., which restricts its household applications.
RU 2124033, Dec. 27, 1998 discloses adhesive mastic comprising water glass (sodium silicate) with the density of 1.38 to 1.41 kg/dm3 and ratio SiO2/Na2O of 2.85 to 3.15, filled by quartz powder with particle size of 0.1 to 0.15 xcexcm, talc with particle size of 5 to 20 xcexcm and linking agent (phurphurol).
This adhesive composition has several considerable drawbacks:
low adhesion strength (about 0.5 to 0.6 MPa);
components toxicity, namely quartz powder particles of the size 0.1 to 0.15 xcexcm irritate mucous membranes of respiratory tract and penetrating blood vessels are practically irremovable from living body. Phurphurol (aromatic aldehyde) irritates skin (permissible concentration in air is 0.05 mg/m3, in waterxe2x80x941 mg/l);
low stability when stored: phurphurol causes solidification, which leads to increase of adhesive paste viscosity and change of its adhesive properties. Moreover poor tixotropic properties of sodium water glass cause sedimentation of solid phase (quartz powder, talc), which leads to mastic segregation. It forces the user to keep components in at least two separate packages. It is inconvenient in practice because the user has to mix components in exact proportions following mixing rules;
poor water resistance due to low stability and solubility of solidified sodium silicate in water.
The closest in details to the claimed invention is the adhesive composition (EP 0 041212, Dec. 09, 1981) comprising sodium silicate aqueous solution with weight ratio SiO2/Na2O 2.6-3.9:1 and/or potassium silicate aqueous solution with weight ratio SiO2/K2O 2-2.6:1 and also 25 to 50% w/w finely dispersed (from 1 to 45 xcexcm) crystallic calcium carbonate originated from metamorphic calcite, 2 to 10% w/w quartz powder with the particle size up to 15 xcexcm and developed specific surface area at least 3.5 m2/g. This composition contains up to 24% w/w of stable aqueous organic polymer dispersion (50% of polymer) such as: acrylate, styrolacrylate, and/or styrolbutadiene. Up to 2% w/w lithium hydroxide is added to this adhesive composition in order to improve water resistance.
This adhesive composition mainly used in industry for adhering mineral fiber tiles has several considerable drawbacks:
low adhesion strength (about 0.5 to 0.6 MPa);
poor activity and properties stability under storage. Calcium carbonate is highly reactive in aqueous solutions of sodium and/or potassium silicates, which leads to thickening and following solidification of adhesive composition. All above upsets stability of viscosity and adhesive properties in a short time after composition preparation and thus complicates its use when stored for a long time;
adhesive composition components toxicity. It is caused by the fact that polymer latexes (acrylic, styrolic, styrolacrylic, butadienic) contain residues of monomers (1 to 2%) and synthetic catalysts (0.1%), and also stabilizers (0.5%) and organic solvents (2 to 5%);
poor thermostability. This is caused by thermal decomposition of calcium carbonate into calcium oxide and carbon dioxide at 300-400xc2x0 C., which leads to adhesion junction breakdown.
Thus proceeding from the prior art, existing adhesive compositions lack the desirable characteristics allowing their use in industry and household. These characteristics include: enhanced storage stability, low toxicity, high adhesion strength, ability to solidify under ambient conditions, possibility to use them for wide range of materials, while keeping high water resistance of adhesive junction.
Accordingly, the object of the present invention is to provide water glass-based adhesive composition having
enhanced adhesion strength;
prolonged activity and storage stability;
pollution-free use;
improved thermostability;
pollution-free adhesive composition fabrication process;
with high water resistance of adhesion junction.